Actually this topic was brought up a few weeks back and I specifically remember Hilariousetc stating that having a minimum requirement for joining will only encourage people to buy/trade merits.

My take on this is that there are a large number of people who post meaningful content but they dont get merits either because they post in sections where merit sources dont patrol or the merit sources ran out of merits. Bottom line is that we need an increased number of merit sources patrolling every section of the forum if we are to make merit as a "criteria" of being selected as a "good poster".

Due to the subjective nature of merit - this is almost impossible to counter.